There has been proposed a related art printer that forms an image electrophotographically, to which a process cartridge can be removably mounted. The process cartridge includes a developing cartridge having a developing roller and a photosensitive cartridge having a photosensitive drum. The developing cartridge is removably mounted to the photosensitive cartridge.
For example, JP-A-2000-250310 describes a related art photosensitive cartridge in which upwardly protruding rotatable rolls are provided at two positions on both the right and left ends of the bottom wall of a case, and urging member is rotatably provided to be able to expand or contract on the inner surface of both the right and left side walls of the case.
If the related art developing cartridge is mounted to the photosensitive cartridge, the rolls receive the case of the developing cartridge at the portions on the lower surface of a downwardly directed, convex curved toner accommodating chamber to reduce unsteadiness of the case.
Further, action parts projecting from both the right and left outsides of the toner accommodating chamber are formed on the case of the developing cartridge, whereby if the developing cartridge is mounted to the photosensitive cartridge, the urging member presses the action parts to press the developing roller via the developing cartridge against the photosensitive member drum.